Halloween is celebrated in America as a result of ancient Celtic traditions combined with Christian influences and later cultural adaptations. It originated from the Celtic festival Samhain, celebrated on November 1, marking the end of the harvest and the beginning of winter. Celts believed that on the night before Samhain, the souls of the dead returned to earth, so people dressed in costumes and lit fires to ward off spirits. In the 7th and 8th centuries, the Christian church created All Saints Day on November 1, making October 31 "All Hallows' Eve," later shortened to Halloween. Irish immigrants brought Halloween traditions like dressing in costumes and trick-or-treating to the United States in the 19th century. Over time, Halloween evolved into the festive holiday America celebrates today, centered on costumes, trick-or- treating, parties, and candy. It is widely enjoyed as a fun, secular celebration for children and adults alike.